University  of  California— College  of  Agriculture, 

AGRICULTURAL  EXPERIMENT  STATION. 

E.  W.  HILGARD,  Director. 


EKINOSE  OE  THE  VINE. 


By  FREDERIC  T.  BIOLETTI  and  E.  H.  TWIGHT. 


VINE  LEAF  AFFECTED  WITH  ERINOSE— UPPER  SURFACE. 

BULLETIN     No.  136. 

(Berkeley,  November,  1901.) 


SACRAMENTO: 
a.  j.  johnston,  :::::::  superintendent  state  printing. 

1901. 


Digitized  by  the  Internet  Archive 

in  2012  with  funding  from 

University  of  California,  Davis  Libraries 


http://www.archive.org/details/erinoseofvine136biol 


ERINOSE  OF  THE  VINE. 


By  FREDERIC  T.  BIOLETTI  and  E.  H.  TWIGHT. 


For  the  last  five  years  specimens  of  vine  leaves  affected  with  Erinose 
have  been  received  at  the  Agricultural  Experiment  Station  in  increasing 
numbers.  The  disease  is  evidently  spreading  rapidly  throughout  the 
vineyards  of  California,  and  the  number  of  inquiries  received  concern- 
ing it  makes  it  desirable  that  an  account  of  it,  available  for  general 
distribution,  should  be  published. 

Erinose  is  a  disease  of  the  vine  characterized  by  swellings  on  the 
upper  surface  of  the  leaves,  and  corresponding  depressions  on  the  lower 
surface.  These  swellings,  when  numerous,  cause  considerable  deforma- 
tion of  the  leaves,  but  not  the  change  of  color  to  yellow  or  brown  which 
is  characteristic  of  most  fungous  diseases.  Even  very  badly-affected 
leaves  retain  almost  their  normal  green  color  until  late  in  the  season. 
The  depressions  on  the  under  side  are  coated  with  a  thick  felt-like 
covering,  which,  at  first  pure  white,  gradually  turns  rusty  and  finally 
becomes  dark  brown.  Generally,  the  swellings  and  corresponding 
depressions  are  isolated  and  few  in  number  on  the  affected  leaves,  but 
in  severe  cases  they  are  numerous  enough  to  become  confluent,  and  the 
whole  lower  surface  is  then  completely  hidden  by  the  felt-like  covering. 
Occasionally,  indeed,  the  felt-like  material  extends  to  the  upper  surface 
in  narrow  strips  bordering  the  veins,  and  may  even  be  found  on  the 
petioles  and  flower  clusters. 

Most  of  the  specimens  received  at  the  laboratory  were  sent  under  the 
impression  that  they  were  attacked  by  a  fungus,  and,  in  fact,  the  coat- 
ing has  a  strong  superficial  resemblance  to  some  fungous  growths.  A 
microscopic  examination  shows,  however,  that  it  consists  of  a  mass  of 
hypertrophied  hairs  or  abnormal  outgrowths  of  the  epidermal  cells  of 
the  leaf.  They  are  larger,  more  abundant,  and  more  persistent  than 
the  normal  leaf-hairs  of  the  leaf,  and  differ  also  in  being  often  branched 
and  usually  unicellular.  This  abnormal  growth,  in  common  with 
similar  growths  found  on  other  plants,  is  called  an  erineum,  from  a 
Greek  word  meaning  woolly.  This  is  the  derivation  of  the  word 
Erinose,  which  means  woolly  disease,  a  very  appropriate  name.  The 
erinea  of  leaves  were  formerly  supposed  to  be  of  fungous  origin,  but  are 
now  known  to  be  due  to  the  attacks  of  minute  mites.  The  stings  or 
punctures  of  these  mites  exert  a  stimulating  effect  upon  the  epidermal 


4  — 


Fig.  1. 
White  patches  of  erineum  on  the  lower  surface 
of  a  leaf  as  they  appear  in  the  earlier  part 
of  the  season. 


Upper  surface  of  a  badly  affected 
leaf,  showing  how  the  erineum 
extends  to  the  upper  surface  in 
severe  cases. 


Fig.  2. 


Lower  surface  of  the  leaf  shown  in  the  frontispiece,  showing  the 
brown  patches  of  erineum  as  they  appear  in  autumn. 


cells  of  the  leaf,  which  causes  them  to  grow  out  into  the  abnormal  hair- 
like processes  already  described.  The  mite  causing  Erinose  of  the  vine 
is  known  as  Phytoptus  vitis,  and  is  related  to  the  mites  causing  a 
similar  disease  of  the  walnut  and  the  leaf-blister  of  the  pear,  both  of 
which  are  very  common  in  California. 

The  Phytoptus  vitis  is  not  a  true  insect,  but  a  mite  or  acarid  belonging 
to  the  class  of  Arachnida  to  which  belong  also  spiders,  scorpions,  ticks, 
and  our  common  clover-mite  or  red  spider  so  destructive  to  fruit  trees. 
These  mites  are  extremely  minute,  and  only  a  practiced  eye  can  perceive 
them,  among  the  tangled  mass  of  erineum  on  the  leaf,  by  the  aid  of  an 
ordinary  hand  magnifier,  and  then  only  with  great  difficulty.  To  see 
them  easily  they  must  be  separated  and  examined  with  a  microscope 
magnifying  at  least  fifty  diameters.  To  isolate  them  the  method  recom- 
mended by  Valery  Mayet  is  probably  the  best.  With  a  sharp  knife 
scrape  off  a  quantity  of  the  erineum  into  a  watch-glass.  As  soon  as  the 
hairs  begin  to  dry-up,  the  mites  abandon  them  and  may  be  found  con- 
gregated in  numbers  around  the  edge  of  the  watch-glass.  The  form 
which  we  usually  find  upon  the  vine  leaves  is  an  elongated,  flexible, 
almost  cylindrical,  worm-like  larva  about  2Z0  °f  an  incn  m  length  and 
g^-g-  of  an  inch  in  diameter.  The  mite  is  furnished  at  one  end  with  four 
legs,  and  is  armed  with  two  piercing  organs,  with  which  it  attacks  the 
leaves.  Notwithstanding  its  small  size  and  apparently  awkward  shape 
it  is  very  lively  in  its  movements  and  shows  remarkable  vitality.  It 
has  been  known  to  survive  an  immersion  of  forty-eight  hours  in  water, 
and  has  been  seen  to  lay  eggs  after  remaining  in  glycerine  for  twenty- 
four  hours.  Like  other  members  of  the  group,  the  Phytoptus  vitis  passes 
through  several  forms,  and,  besides  the  common  larva  already  described, 
has  at  different  stages  of  its  metamorphosis  six  and  eight  legs,  the  latter 
being  the  perfect  form.  The  four-legged  larvae  pass  the  winter  under 
the  rough  bark  of  the  vine  or  among  the  scales  of  the  buds,  many  of 
them  without  change  of  form,  while  others  surround  themselves  with  a 
kind  of  transparent  cyst. 

Amount  of  Injury. — Erinose  was  formerly  considered  to  be  a  very 
serious  disease  of  the  vine,  owing  to  the  fact  that  its  effects  were  con- 
fused with  those  of  the  powdery  mildew.  It  is  only  in  very  exceptional 
cases  that  it  is,  alone,  capable  of  doing  serious  injury  to  the  vine  or  its 
crop.  When  accompanying  oidium  or  drought  it  may,  however,  per- 
ceptibly increase  the  damage  due  to  these  causes.  When  very  abundant, 
it  may  seriously  interfere  with  the  growth  of  young  vines,  but,  according 
to  Mayet,  never  damages  old  vines,  except  by  interfering  slightly  with 
the  ripening  of  the  canes  or  at  most  causing  an  almost  imperceptible 
diminution  of  crop.  All  varieties  of  vines  are  not  equally  attacked. 
According  to  Ravaz,  certain    American    species   such   as   Berlandieri, 


—  6  — 


Fig.  3.  Photomicrograph  of  a  cross-section  through  an  affected 
area  of  a  vine  leaf,  showing  the  erineum  in  the  depression 
on  the  lower  surface.  The  broken  line  shows  the  position 
that  this  portion  of  the  leaf  would  have  occupied  had  it  not 
been  attacked  by  the  mites. 


Fig.  4.    Vine  affected  with  Erinose. 


Mustang,  Cinerea,  Cordifolia,  and  Scuppernong  are  immune.  All  varie- 
ties of  vinifera  are  susceptible,  but  not  equally.  Of  varieties  cultivated 
in  California,  Sauvignon,  Sirah,  Marsanne,  and  Gamay  Teinturier  are 
said  by  Ravaz  to  be  little  subject  to  attack,  while  Aramon,  Cinsaut,  and 
Frontignan  (Small  Muscatel)  are  very  susceptible.  The  worst  cases  so 
far  observed  in  California  have  been  on  Flame  Tokay  and  Mission3  but 
it  has  been  found  also  on  other  varieties,  among  them  Zinfandel  and 
Muscat. 

Methods  of  Treatment. — Since  sulfuring  the  vines  for  the  treatment  of 
oidium  has  become  general  in  France  there  has  been  little  trouble  with 
Erinose.  The  phytoptus  seems  as  sensitive  to  the  fumes  of  sulfur  as  the 
red  spider,  and  several  sulfurings  during  the  late  spring  and  early  sum- 
mer are  recommended  for  the  control  of  the  mite.  The  only  vineyards 
which  have  been  found  badly  affected  in  California  are  those  in  which 
little  or  no  sulfuring  has  been  done,  or  those  where  the  growth  of  foliage 
has  been  so  luxuriant  as  to  prevent  the  evaporation  of  the  sulfur  by  the 
sun.  In  the  latter  cases  the  vines  are  so  strong  that  they  practically 
receive  no  harm  from  the  disease.  In  severe  cases  a  winter  treatment 
of  the  vine  stumps  is  practiced  in  France.  This  treatment  consists  in 
pouring  about  one  quart  of  boiling  water  over  the  stump.  For  very 
large  stumps  a  somewhat  greater  amount  of  water  is  used,  and  for 
smaller  vines  a  proportionate  amount.  This  method  is  said  to  be  very 
efficacious,  and  with  the  portable  boilers  constructed  for  the  purpose 
two  men  can  treat  from  1500  to  2000  vines  per  day.  Cuttings  taken 
from  affected  vines  for  the  purpose  of  rooting  or  grafting  may  be 
thoroughly  disinfected  by  placing  them  in  hot  water  (122°  F.)  for  ten 
minutes.  If  this  is  done  carefully  all  the  mites  and  their  eggs  will  be 
destroyed  without  injury  to  the  cuttings. 

Distribution  in  California. — The  first  specimens  of  Erinose  received 
by  the  Experiment  Station  were  sent  from  Windsor,  Sonoma  County, 
in  1896.  The  next  year,  affected  leaves  were  received  from  Healdsburg 
and  Dry  Creek,  in  the  same  county.  All  these  cases  were  upon  Mis- 
sion vines.  Since  then,  specimens  of  the  disease  have  been  received  as 
follows:  1898,  from  Kenwood,  Sonoma  County,  on  Zinfandel;  1899, 
from  Lytton  and  Sebastopol,  Sonoma  County;  1901,  from  Martinez, 
Contra  Costa  County,  Roseville,  Placer  County,  Florin  and  Folsom, 
Sacramento  County,  Cloverdale,  Sonoma  County,  and  from  Dinuba, 
Tulare  County. 

A  short  account  of  this  disease  was  given  in  the  fifth  biennial  report 
of  the  California  State  Board  of  Horticulture,  on  page  50,  where  its 
occurrence  is  noted  at  Florin,  Sacramento  County. 


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